In Thailand, most migrant labor from rural districts to Bangkok Metropolis are young workers in their late teens and twenties. Nevertheless, expected urban wages for young migrants are lower than elder ones and uncertainty of wage, in turn, is greater as the migrants become younger. This paper explains the migration behavior that is particularly intensive among youth with regard to workers' motive for learning about their own ability or suitability to different jobs. Uncertainty of urban wages reflects innate ability that is unobservable to workers themselves, hence indicating that wages are better signals of such heterogeneity for younger migrants. This implies young workers' migration to Bangkok is motivated by learning about own ability/suitability. Empirical findings using labor survey data from Thailand show that; (1) Bangkok wages for younger migrants are more diverse from being more dependent on unobserved attributes, and (2) the wage diversity due to its dependence on ability motivates young workers' migration to Bangkok